The present invention relates to a method for forming an organic semiconductor film used in thin film transistors or the like using organic semiconductor materials.
Organic semiconductor elements having organic semiconductor films (organic semiconductor layers) comprising organic semiconductor materials are used in devices using logical circuits such as TFTs (thin film transistors), RFIDs (RF tags), or memory used in liquid crystal displays or organic EL displays due to their ability to reduce weight, lower cost, and enhance flexibility.
In the production of an organic semiconductor element, one known method of forming an organic semiconductor film is a wet process such as a coating method using a coating prepared by dissolving an organic semiconductor material in a solvent.
In addition, in order to obtain an organic semiconductor film with high mobility, it is important to enhance the crystallinity of the organic semiconductor film. Therefore, various methods of improving the crystallinity of an organic semiconductor film have also been proposed in the formation of an organic semiconductor film by means of a wet process.
For example, WO 2007/119703 illustrates a method of forming an organic semiconductor film with good crystallinity with an example by applying a solution prepared by dissolving an organic semiconductor material in a solvent to a supporting member so as to form a solution film and then evaporating the solvent from the interface at the edge of the solution film that is formed, thereby moving the interface of crystal growth and forming an organic semiconductor film.
JP 2005-508515 A describes a method for drying an organic semiconductor film, wherein the treatment time is reduced in the formation of an organic semiconductor film using such a solution containing an organic semiconductor material by combining a solution film coating step and a drying step involving infrared irradiation.
In addition, focused or non-focused infrared/near-infrared laser beams with a wavelength of from 0.7 to 2 μm are illustrated with an example as infrared rays.
Furthermore, JP 2005-211769 A describes a substrate production device which, in the production of an organic EL element or the like, controls the drying process of a solution film (droplets) so as to form a dry thin film with excellent film thickness uniformity and high flatness by applying a solution containing an organic semiconductor material to a substrate and then selectively irradiating designated areas with electromagnetic waves.
Infrared light with a wavelength of from 0.8 to 20 μm is illustrated with an example as electromagnetic waves used to dry such a solution film. JP 2005-211769 A further describes that by using infrared laser beams as electromagnetic waves, the central part is selectively dried in the early stages of drying, and the concentration of energy gradually weakens thereafter so that the energy is dispersed in the latter half of the drying process, which enables uniform drying.
However, the demand for the formation of organic semiconductor films has become even more intense in recent years, and there is a demand for the emergence of a method capable of stably forming an organic semiconductor film which has better crystallinity and with which a semiconductor element with high mobility can be obtained.
An object of the present invention is to solve the problems of such conventional technology and to provide a method for forming an organic semiconductor film capable of stably forming an organic semiconductor film having good crystallinity and high mobility.